Wall Insulation

Improving Energy Efficiency on Exterior Walls

When it comes to upgrading the insulation, or maybe adding some for the first time, in older homes there are several choices for homeowners to choose from.

Although it would seem easier to remove the wall covering or the siding covering and install insulation brand new, there usually are several factors that would prevent this. We are going to look at several of the popular options.

The four main options are loose cellulose, dense-packed cellulose, loose blown-in fiberglass, and dense-packed fiberglass.

All these choices have pros and cons, and we are going to look at each one. Depending on your situation and how your wall structure is, we would determine which method is right for you.

Loose-fill cellulose

Loose-fill cellulose is the insulation we would recommend for the attic insulation. This type of insulation upgrade was popular 30-40 years ago, and now with the Green Movement has become one of the most popular insulation products in the United States today. Since cellulose is made up of moslty recycled paper, it is the leader in green insulation. Studies done on cellulose also suggest that cellulose may actually aid in protecting a building from damage in a fire over fiberglass. The reasoning is that cellulose is a denser material compared to fiberglass. This tighter fit doesn’t allow the oxygen through starving the flames.

When it is installed in a wall cavity, we would expect some settling to occur (average of 20%) but still maintains it’s overall R-Rating. Being made of small particles, they form tighter around penetrations creating a tighter fit. A tighter fit reduces the stack effect that occurs in homes. It is usually installed from a hole drilled into the wall from the interior or the exterior. These holes would be at the top and bottom of each cavity so that it could be blown both up and down into the cavity.

Dense-packed cellulose

Dense-packed cellulose is the contractors choice for insulating old homes. It is essentially taking loose cellulose and blowing it into a wall cavity until it reaches 3.5 lbs. per cubic foot, which makes it dense. Not an easy project to do and requires a special machine and years of training. The R-value is comparable to loose cellulose, however since it is densely packed in the cavity the air flow is minimized. Often it’s not the lack of r-value in your home that makes you cold but the draft that comes through from the air infiltration. Dense-pack insulation shouldn’t be installed against brick or concrete walls since those walls hold moisture.

Loose-fill fiberglass

Loose-fill fiberglass is popular with “do-it-yourselfer’s”. The material can be purchased at many big box stores and if enough quantities are purchased, the blowing machine rental is included free of charge. Although an in-expensive solution for DIY’s, the results sometimes don’t justify the effort. When loose fill fiberglass is installed in walls, the drawbacks include uneven density and the lack of stopping air leaking through the heating envelope. There are health concerns associated with inhaling glass insulation fibers, but there currently are no regulations. It is a good idea to avoid breathing in the fibers, and not ideal in areas where they may be in constant disturbance.

Loose fiberglass can be blown in quite tightly, and when blown to a high density (at least 2 lbs. per cubic foot), will result in a reduction of air leakage through the wall (like dense-packed cellulose). We talk about dense-packed fiberglass next.

Dense-packed fiberglass

Taking fiberglass fibers and sending them through a high velocity fan and into wall cavities is a better solution than installing loose fill fiberglass. Since this fills cavities at high capacity, it is normally done by professionals. Not as popular as cellulose, but with recent technology advancements is becoming more popular in certain applications. It has excellent thermal and acoustical performance, and is non-corrosive and non-combustible. The main drawback is that it has a lower r-value per inch in addition to the health concerns mentioned above.

American Home Consultants has been Dane County’s trusted insulation contractor for over a decade. We are a full-service company offering energy assessments, energy audits, home energy tests, and energy ratings. Our insulation department specializes in blown in attic insulation consisting of cellulose or loose fill fiberglass, sidewall insulation using dense pack or spray foam. Attic air sealing using 2-part spray foam, and box sill insulation in the basement.